In order to switch an imaging mode of an imaging optical system between normal imaging and close-up imaging, it has been necessary to use such a method as constituting the imaging lens by a plurality of lenses and moving at least one lens of the plurality of lenses along an optical axis (JP-A-10-104491) or attaching another lens to the front of the imaging lens (JP-U-3094156) at the time of switching the imaging mode from normal imaging to close-up imaging.